The ever-increasing prevalence of bacteria harboring extrachromosomal elements or plasmids that confer resistance to chemotherapeutic drugs, that specify production of hemolysins, bacteriocins, toxins and other invasins and/or that alter biochemical traits so as to make clinical identification difficult, is causing treatment of bacterial infectious diseases to be increasingly more difficult and therefore constitutes a threat to the public health. The objective of our research is to study transmission and functions of plasmids in gram-negative bacteria so as to be able to develop means for effective control and treatment of bacterial diseases. Most of the research will be concerned with R plasmids in Esherichia coli and Salmonella typhimurium and will utilize minicell-producing strains of both of these bacterial species. During the coming year, we will specifically investigate: a) the genetic and biochemical nature of cell-cell interactions between donor and recipient strains leading to plasmid transfer; b) the mechanism of conjugal replication and transfer of plasmids; c) the relationship between chromosomal and plasmid replication in synchronously dividing populations of bacterial cells; d) the possible origins of plasmid replicons leading to the evolution of new plasmid types; e) the patterns of expression of plasmid genes in minicells; f) the utility of using live Salmonella minicells as a vaccine to provide protective immunity; and g) the use of antibodies against drug-inactivating enzymes as a means for the rapid identification of drug-resistant plasmid-containing strains of bacteria. We will utilize the technologies of microbial genetics, molecular biology, immunology and electron microscopy in this research.